1. Field of the Invention
The invention is directed to a plain bearing of the type having a bearing gap filled with liquid metal, with two plain bearing parts each having a surface contiguous with the liquid metal, the surfaces contiguous to the liquid metal lying on one another so as to form a gap connecting the bearing gap with the surrounding space.
2. Description of the Prior Art
Plain bearings having a bearing gap filled with liquid metal, or liquid metal plain bearings for short, are used, for example, in X-ray tubes in order to provide bearings for the rotating anode, and are normally incorporated into the interior of the vacuum housing of the X-ray tube (see e.g. German OS 28 52 908 or European Application 0 479 197). Alloys of gallium, indium or tin, liquid at room temperature, are as a rule used as the liquid metal. Alloys of this sort are highly reactive substances. It is therefore undesirable for liquid metal plain bearings to lose liquid metal. This is particularly true when used in X-ray tubes, since drops of liquid metal that leave the area of the anode can endanger the high-voltage strength of the X-ray tube.
In an X-ray tube having a rotating anode, known from European Application 0 373 705, the surfaces, arranged opposite one another, of a rotor that is connected to the rotating anode and rotates with it, as well as the surfaces of a stationary carrier part, are provided with a layer of a material (gold) that is effective as a wetting agent for the liquid metal and binds reactively with it. This prevents drops of liquid metal that emerge from the liquid metal plain bearing, which is provided as a bearing arrangement for the rotating anode, from leaving the area of the anode.
In the liquid metal plain bearing known from European Application 0 141 476, the surfaces in question are provided with a coating of titanium oxide, which is effective as an anti-wetting agent for the liquid metal, in order to prevent the emergence of liquid metal through a gap located between two plain bearing parts lying on one another. Though it is true that this coating effectively prevents the emergence of liquid metal from the bearing gap, the danger nonetheless exists at the same time that gases can penetrate into the filled liquid metal plain bearing and form dangerous gas bubbles. In liquid metal plain bearings provided for X-ray tubes, this danger of course exists only if the vacuum housing of the X-ray tube is not properly evacuated.